1. Field of the Invention
The present invention relates to a sound field correcting apparatus which is connected to an output of a decoder to reconstruct audio signals of a plurality of channels from audio signals of two channels.
2. Description of the Related Art
There has been known a decoder to produce audio signals of a right channel, a left channel, a center channel, and a rear channel from audio signals of two channels. The audio signals of the two channels have been formed by an encoder such as an MP (motion picture) matrix encoder or the like.
In the decoder, for instance, the audio signals of two channels comprising an L total (L.sub.t) output component and an R total (R.sub.t) output component which are obtained by the MP matrix encoder are reconstructed to audio signals of four systems. However, even if the matrix process executed by the encoder is resolved as it is, enough separation is not derived. Therefore, there is a decoder using a steering emphasis technique to apply an emphasis proportional to an intensity to a preferential direction in consideration of a sound field priority in order to sharply localize a sound image in a desired direction and to obtain a stereophonic feeling. For example, a Dolby pro logic decoder has been known. To emphasize the steering, it is necessary that the sound which responds to the orientation is selected. When such a sound is defined as a dominant sound, the dominant sound can be summarized as a most conspicuous sound in the mixing at a certain moment. It is considered that the dominant sound to discriminate a subjective separation comes from one direction at a time. A capability such that the listener can hear and distinguish the orientations of the other inferior sounds at that moment is limited by the dominant sound. On the other hand, in the case where the audio signals are reproduced by a similar sound volume such that two or more sound cannot be simultaneously masked, a separating process is unnecessary, so that it is also unnecessary that the steering emphasis to improve the localization operates.
In the Dolby pro logic decoder, a preferential value is detected. Since the dominant sound can be resolved into coordinate numerical values by an LR axis and a CS axis which perpendicularly cross each other even if the dominant sound exists in any vector direction of 360.degree., the steering emphasis is independently detected every axis.
The Dolby pro logic decoder has been disclosed in detail in "JAS Journal", Japan Audio Society, pages 22-26, May, 1989.
There has also been proposed a sound field correcting apparatus for falsely obtaining a presence as in a theater by adding reflection sound signals to the audio signals of right and left channels R and L, a center channel C, and a rear channel S which are generated from the decoder as mentioned above.
However, in such a sound field correcting apparatus, if the reflection sound signals are added, a sound image which has been localized by executing the steering emphasis in the decoder becomes dull. Thus, there are problems such that a large extent feeling cannot be obtained and a proper extent feeling and a sound image movement cannot be derived as a reproduction sound for a video image such as a movie or the like.